Dipeptidyl peptidase IV (DPIV) is a serine protease which cleaves N-terminal dipeptides from a peptide chain containing, preferably, a proline residue in the penulitimate position. Although the biological role of DPIV in mammalian systems has not been completely established, it is believed to play an important role in neuropeptide metabolism, T-cell activation, attachment of cancer cells to the endothelium and the entry of HIV into lymphoid cells.
Likewise, it was discovered that DPIV is responsible for inactivating glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide also known as gastric-inhibitory peptide (GIP). Since GLP-1 is a major stimulator of pancreatic insulin secretion and has direct beneficial effects on glucose disposal, in WO 97/40832 and U.S. Pat. No. 6,303,661 inhibition of DPIV and DPIV-like enzyme activity was shown to represent an attractive approach e.g. for treating non-insulin-dependent diabetes mellitus (NIDDM). It is an aspect of the present invention to provide new DPIV inhibitors which are effective e.g. in treating conditions mediated by inhibition of DPIV and DPIV-like enzymes, pharmaceutical compositions e.g. useful in inhibiting DPIV and DPIV-like enzymes and a method of inhibiting said enzyme activity.
Another aspect of the invention relates to a method of treatment, in particular to a method for the treatment of diabetes mellitus, especially non-insulin dependent diabetes (NIDDM) or Type 2 diabetes and conditions associated with diabetes mellitus and to compositions for use in such method.
Dipeptidyl peptidase IV (DPIV) is a post-proline (to a lesser extent post-alanine, post-serine or post-glycine) cleaving serine protease found in various tissues of the body including kidney, liver, and intestine.
It is known that DPIV inhibitors may be useful for the treatment of impaired glucose tolerance and diabetes mellitus (International Patent Application, Publication Number WO 99/61431, Pederson R A et al, Diabetes. 1998 August; 47(8):1253-8 and Pauly R P et al, Metabolism 1999 March; 48(3):385-9). In particular WO 99/61431 discloses DPIV inhibitors comprising an amino acid residue and a thiazolidine or pyrrolidine group, and salts thereof, especially L-threo-isoleucyl thiazolidine, L-allo-isoleucyl thiazolidine, L-threo-isoleucyl pyrrolidine, L-allo-isoleucyl thiazolidine, L-allo-isoleucyl pyrrolidine, and salts thereof.
Further examples for low molecular weight dipeptidyl peptidase IV inhibitors are agents such as tetrahydroisoquinolin-3-carboxamide derivatives, N-substituted 2-cyanopyroles and -pyrrolidines, N-(N′-substituted glycyl)-2-cyanopyrrolidines, N-(substituted glycyl)-thiazolidines, N-(substituted glycyl)-4-cyanothiazolidines, boronyl inhibitors and cyclopropyl-fused pyrrolidines. Inhibitors of dipeptidyl peptidase IV are described in U.S. Pat. No. 6,011,155; U.S. Pat. No. 6,107,317; U.S. Pat. No. 6,110,949; U.S. Pat. No. 6,124,305; U.S. Pat. No. 6,172,081; WO 99/61431, WO 99/67278, WO 99/67279, DE 198 34 591, WO 97/40832, DE 196 16 486 C 2, WO 98/19998, WO 00/07617, WO 99/38501, WO 99/46272, WO 99/38501, WO 01/68603, WO 01/40180, WO 01/81337, WO 01/81304, WO 01/55105 and WO 02/02560, the teachings of which are herein incorporated by reference in their entirety concerning the inhibitors, their production and their use.